"The sights were simply magnificent, beyond any visual experience that I had ever been exposed to," Armstrong once said.

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Media captionBuzz Aldrin: "The aerospace world will be saddened"

'Reluctant hero'

Mr Aldrin told the BBC's Newshour programme: "It's very sad indeed that we're not able to be together as a crew on the 50th anniversary of the mission… [I will remember him] as a very capable commander."

Apollo 11 was Armstrong's last space mission. In 1971, he left the US space agency Nasa to teach aerospace engineering.

Born in 1930 and raised in Ohio, Armstrong took his first flight aged six with his father and formed a lifelong passion for flying.

He flew Navy fighter jets during the Korean War in the 1950s, and joined the US space programme in 1962.

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Media captionPresident Obama described him as "one of the greatest American heroes of all time"

Correspondents say Armstrong remained modest and never allowed himself to be caught up in the glamour of space exploration.

"I am, and ever will be, a white-socks, pocket-protector, nerdy engineer," he said in February 2000, in a rare public appearance.

In a statement, his family praised him as a "reluctant American hero" who had "served his nation proudly, as a navy fighter pilot, test pilot, and astronaut".